Tyagi Kapil Dev, Kumar Arun, Bahl Rajendar, Singh Karmjeet «Experimental measurement of acoustic properties in snow» Акустический журнал, 63, № 3, с. 297-301 (2017)

This paper presents the results of field experiments done for the measurement of attenuation constant and speed of sound in the snow medium. The field experiments were conducted at two locations corresponding to relatively dry and wet snow. The main objective of our method is to overcome the potential limitations of the other methods. There are two major concerns: one is sound signal leakage and the other is the measurement need to be done within a same layer of snowpack. The ref lections from the boundaries will affect the measurements. In our experiments the transducers are kept far from the snowpack boundaries, so that there will be no likelihood of strong ref lected signals from the boundaries. These issues have not been addressed by the other researchers. This work adds to the measurement results of the attenuation constant and speed of sound in snow that are available in the research literature. It is found that sound signal attenuation greatly depends on the frequency of sound signal and wetness of snow.

Xu Shi-da, Li Yuan-hui, Liu Jian-po «Detection of cracking and damage mechanisms in brittle granites by moment tensor analysis of acoustic emission signals» Акустический журнал, 63, № 3, с. 359-367 (2017)

An acoustic emission (AE) testing of rock cracking was performed under uniaxial loading conditions by precut varisized circular holes in selected brittle granites. Based on AE-source location technique and AE-theory for moment tensor analysis, rules of the temporal–spatial evolution of micro-cracks in different failure mechanisms were explored and types of micro-cracks were analyzed as well. The results revealed that the micro-cracks are uniquely easy to generate in the positions where stress are concentrated. Tensile fractures are easy to form on the roof and floor of a circular hole, while shear fractures are easy to be found on both sides. The locations of initial cracks generated around the holes in the loading process are the direction or vertical direction of maximum principle stress. Macroscopic crack orientation agrees with the direction of maximum principle stress approximately. As the size of circular opening increases and the relative size of pillar decreases, shear cracks are dominant with the percentage more than 45%, tension cracks are fewer, accounted for less than 40% of the total events, and mixed-mode cracks represent a minimum proportion, despite the decrease of percentage of shear cracks. The findings of this work can serve for supporting design of tunnel or roadway to avoid collapse.